Pressure sensitive adhesive tape and disposable diaper

ABSTRACT

Pressure sensitive adhesive tape having a backsized, reinforced fibrous backing, a pigmented, plasticized polyvinyl chloride backsize, a release coat of silicone rubber, and an aggressively tacky adhesive of a block copolymer of isoprene and styrene tackified with a polyolefin and plasticized with an extended oil. Particular utility as a disposable diaper fastener is disclosed.

United States Patent 1191 Schmidt Mar. 19, 1974 [5 PRESSURE SENSITIVEADHESIVE TAPE 3.464.848 9/1969 Hechlman ct a1 117/122 PB AND DISPOSABLEDIAPER 3,625,752 12/1971 Korpman 117/122 PA 3,660,323 5/1972 Raguse117/122 PA [75] In entor: Ge ge Schmldl, enah, W1s. 3.681.190 8/19721331111 11151 117/122 PA 3,740,366 6/1973 Sanderson et al..... 117/122PB 1731 Asslgnee' corporatmn 3,630,201 12/1971 Endres .1 128/287 [22]Filed: Feb. 1, 1973 Primary ExaminerCharles F. Rosenbaum Attorney,Agent, or Firm-Daniel J. Hanlon, Jr.; Wil- [zl] Appl' 328731 liam D.Herrick; Raymond J. Miller [52] US. Cl. 128/287, 117/122 PA [57]ABSTRACT [51] Int. Cl A411) 13/02 I I [58] Field of Search, 128/156117/122 R Pressure sensitive adhesive tape having a backsized. 7 117/122IZZPA 122 reinforced fibrous backing, a pigmented, plasticized polyvinylchloride backsize, a release coat of silicone [56] References Citedrubber, and an aggressively tacky adhesive of a block copolymer ofisoprene and styrene tackified with a UNITED STATES PATENTS polyolefinand plasticized with an extended oil. Partic- :endncks "l ular utilityas a disposable diaper fastener is disclosed. orpman 3,161.533 12/1964Gaynes 117/122 PA 10 Claims, 3 Drawing Figures PATENTEDNAR 19 m4 FIG. 3

FIG. 2

PRESSURE SENSITIVE ADHESIVE TAPE AND DISPOSABLE DIAPER BACKGROUND OF THEINVENTION In the manufacture of disposable diapers it has provendesirable to have positive fastening means other than ordinary safetypins. From the point of view of both safety and convenience, such animproved fasteneris advantageous. Especially desirable is an improvedfastener that is both economical and forms an integral part of thediaper. I

It has been suggested that strips of ordinary pressure sensitiveadhesive tape would serve this purpose. However, most conventional tapesof this type do not have a sufficiently aggressive adhesive to remainadhered during normal use to the surface of polyolefin films such aspolyethylene which are commonly used as impervious backings for suchdiapers. The problem is further aggravated when an embossed film is usedto provide more attractive feel and appearance. Consequently, whenordinary tapes are used as fasteners in the form of attachment strips,the strips frequently become detached prematurely before the diaper isready for use. In addition, once the diaper is in place on the wearer,if the adhesive does not adhere firmly, the fastening strip may becomeloose and therefore be ineffective. When tack is increased to overcomethese premature detachment problems, another problem arises in trying toprovide a suitable protective release strip for temporarily covering theadhesive on the unattached half of the fastening strip.

Conventional release strips for covering pressure sensitive adhesivesare designed for easy release. In certain instances, as a result, thesesheets tend to become displaced prematurely during handling of thediaper, uncovering the adhesive mass and causing it to stickinadvertently to a wrong portion of the diaper or to an adjacent diaperin a package, whereupon these diapers may be rendered useless. If therelease sheet is designed with sufficient adherent power to stay inplace prior to using the diaper, it sometimes is difficult to remove thesheet without tearing the other end of the strip from the diaperbacking, or causing transfer of adhesive to the protective strip, orrupturing the tape itself. It is highly desirable, therefore, to providea pressure sensitive adhesive tape for diaper fastening purposes inwhich one end adheres firmly to the film backingof the diaper and thefree end lends itself to easy release from a protective cover stripwithout destroying the adhesive power of the pressure sensitive mass.

With this invention there is disclosed a pressure sensitive adhesivetape adapted for use with disposable, film-backed diapers which adheresto the film backing with sufficient firmness to insure againstdisplacement in normal handling and which, when provided with aprotective cover sheet, can be detached therefrom without damage to thetape, the adhesive mass, or the diaper.

SUMMARY OF THE INVENTION Pressure-sensitive tape strips normally foundsuitable for use with disposable diapers usually have a width of fromabout A inch to #4 inch and a length of fromabout 2% inches to 3 inches.These tapes are ordinarily supplication to the diaper.

The backing designed for use in making such tapes must be able towithstand tear and tensile forces not normally encountered by pressuresensitive adhesive tapes. As the wearer twists and turns or makes othernormal movements, substantial forces are applied across the narrowdimension of the tape in varying directions and degrees. Many commontape backings lack suitable strength characteristics to withstand theseunusual use requirements, and special attention must, therefore, begiven to providing higher tear and tensile properties.

In addition to having the above requirements with respect to tensile andtear, the tape must have sufficient adhering power to the surface ofpolyethylene or similar films used for the diaper backing so that itdoes not release prematurely. A tape having such adhering strength willtear the diaper backing (usually a polyethylene film 1 mil thick) ratherthan release therefrom, when the stress is applied in shear.

The pressure sensitive adhesive utilized for the tape of my inventionincludes a block copolymer of isoprene and styrene tackified with apolyolefin and extended with an oil.

Since the preferred tape arrangement for application to disposablediapers is in roll form, the tape must be capable of being rolled andstored for an extended period prior to use without blocking. Liners maybe used to prevent blocking but, because of cost, are generally to beavoided. I prefer to use a release coat which provides for easy unwindwithout adhesive transfer.

The release coat of the tape of the invention utilizes a silicone rubberwhich may include controlled release additives. A backsize coating isalso desirable to provide a suitably smooth surface and a barrier to theundesirable penetration of the release coating into the tape backing. Abacksize composition consisting of a blend of polyacrylate and polyvinylchloride has been found suitable. The backsize coating may be pigmentedfor increased opacity and for a pleasing appearance.

A further requirement of the tape is that it be easily releasable fromthe protective release strip applied to the unattached tape portion. Thetape must stick to the release strip during normal handling but bereadily separated at the time the diaper is used. An example of aprotective release strip is a polyethylene film having raisedembossments of limited area and applied to the adhesive in a manner suchthat the raised portions contact the adhesive. In this manner thecontact area and, therefore, the effective level of adherence of the'tape to the release strip is reduced]. Thus the embossed release stripremains attached to the tape prior to use and yet is easily removed whennecessary.

When the raised embossments comprise approximately a third of the totalsurface area of the release strip, the degree of adhesion between thetape and the strip usuallyfalls within the acceptable range. Suitablyconstructed release strips of other types consisting of paper or polymerfilms, with or without embossing, and if necessary coated with a releasematerial (e.g., a silicone) may also be used.

In summary, my invention comprises a pressure sen sitive adhesive tapehaving (I) a reinforced fibrous backing, (2) an aggressive adhesivebased on an isoprene-styrene block copolymer, a resinous tackifierpreferably of the polyolefin type, and a suitable extension oilpreferably of the naphthenic variety, (3 a polyacrylate plasticizedpolyvinyl chloride backsize, and

(4) a release coat based on a silicone rubber. The tape has particularutility in combination with a protective sheet as a fastener fordisposable diapers.

Accordingly, the primary object of the invention is to provide a unique,aggressively tacky pressure sensitive adhesive tape having desirabletear and tensile strength properties.

Another object is to provide such a pressure sensitive adhesive tapethat is especially suited for use as a disposable diaper fasteningdevice.

These and other objects will become more apparent upon reference to thefollowing specification and drawings wherein there are described variousselected embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view in partialsection of a pressure sensitive adhesive tape according to thisinvention, and

FIGS. 2 and 3 illustrate the tape of the invention in combination with adisposable diaper and protective sheet.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The exact physical strengthrequirements for a diaper tape depend upon a complicated array offactors, but it is known that some tapes having tensile strengths ashigh as lbs/inch width in the long direction of the tape tab have failedin use. Because of production machine considerations, it is desirable tocut the tabs from a supply roll having a width corresponding to the longdirection of the tabs. This puts the major tensile stress in the weakerdirection of paper webs, and the major tearing stress is also in anunfavorable direction. This makes the tape backing requirements quitesevere. It is interesting to note that even on very weak film diaperbackings, tapes fail while the backing remains intact. These failuresresult from a complex variety of stresses some of which are applied athigh rates of speed. Undoubtedly failure is sometimes the result of aseries of stresses, each of which disrupts some of the fiberbinderstructure in the tape backing until failure finally occurs. Regardlessof the mechanism by which failure occurs, it has been found that tapebases having CD (cross direction) tensile strengths above 25 lbs./inch,along with an elongation above about 10% in the same direction, haveadequate strength for use on diapers. The tensile and elongation areboth very sensitive to rate of application of stress, and these limitsare for tape bases strained at 12 inches per minute on a 5 inch span.This measure of elongation provides the toughness needed to prevent theinitiation of a tear. Generally the basis weight of saturated backingsused in the present invention is in the range of from 50 to 120lbs/3,000 ft preferably 60 to 90 lbs/3,000 ft.

The adhesive for a good diaper tape must, of course, have good adhesionto polyethylene film. It must also have good shear resistance, sincemost of the force exerted on the tape is parallel to the length of thetape tab. An adhesive system based on styrene-isoprene block copolymerssuch as are described in US. Pat. No. 3,239,478 for example, andspecifically Kraton l 107 (Shell Chemical Company) has been found to besatisfactory. The elastomer may be tackified with a variety ofconventional tackifiers to give good adhesion to polyethylene film.However, the adhesives prepared without further compounding arecharacterized by a harsh or jerky peel as well as low quick stick, asdefined below. Inclusion of rubber extension oils, which serve asplasticizers, correct this deficiency. An antioxidant must be includedas is the usual practice in pressure sensitive systems. Fillers may alsobe used but are not essential. In general, adhesive coating weights offrom about 0.8 to 1.8 oz. per square yard can be used, but weightswithin the range of from about 1.0 to 1.5 oz./yd. provide the bestcompromise of cost and performance.

Adhesive tests used to characterize the tapes of this invention includesthe standard tests of the Pressure Sensitive Tape Council (PSTC) asdescribed in Test Methods for Pressure Sensitive Tapes, 6th ed.,Specifications and Technical Committee, Pressure Sensitive Tape Council:Peel Adhesion (PSTC-l) and Quick Stick (PSTC-S), as well as modifiedtests to study adhesion to polyethylene and Quick Stick to polyethylene.To measure adhesion to polyethylene, the same polyethylene film used indisposable diapers was fixed to steel panels by first applying to thepanels an unsupported, pressure-sensitive adhesive film. This adhesivewas transferred from release paper which was removed and the exposedadhesive covered with diaper liner. The resulting panels were used onlyonce. Tapes were applied to the film-covered ,steel panels and QuickStick to polyethylene determined just as in PSTC-S. Adhesion topolyethylene was measured on panels prepared in the same way, but thetest samples were rolled as inPSTC-l before testing. The actual peeltest was run at a angle using the same jig used in PSTC-S.

Shear resistance has been measured by the standard PSTC-7 procedure,modified by tilting the apparatus 10 from vertical so that a peelcomponent is introduced into the test. It has been found that actual usefailures occur with adhesives having rather high shear ratings. Byintroducing peel forces simultaneously with shear, such adhesives oftenshow a weakness in holding power.

EXAMPLE 1 An 80 Ib./3,000 sq. ft. kraft tape base, beater treated withnitrile rubber, manufactured by Premoid Corporation, is a suitable tapebase. This base was backsized with the following backsizeformulatiomusing a coating weight of 15 lb./3,000 sq. ft. (In theseexamples, parts are by weight unless otherwise noted.)

Rhoplex B 15 (a trademark for a polyacrylate emulsion from Rohm & Haas)75 Acetic Acid 0.07

Geon 352 (trademark for a polyvinyl chloride emulsion from B. F.Goodrich) 25 TiO A release coat was then applied over this backsizeusing the following silicone coating:

Syl-Off 23 (trademark-Dow Corning Corp.) 25

Perchlorethylene Syl-Off 297 (trademark-Dow Corning Corp.) 0.6

Dow Corning C-4-2l l7 0.9

Dow Corning 176 0.9

All the active ingredients of this formulation are sold by Dow CorningCorporation. Approximately 0.9 lbs/3,000 sq. ft. of the silicone coatingwere applied and well cured by heating to approximately 400 F for a fewseconds.

The release coated sheet was next coated with the following adhesivecomposition:

Kraton 1107 (styrenedsoprene block polymer from Shell Chemical Co.) 100Sta-Tac 100 (a polyolefin tackifier from Reichhold Chemical Co.). I25Di-t-butyl-p-cresol (antioxidant) 2 Sunthene 3120 (a naphthenic oil fromSun Chemical Co.) 25 Hydrated alumina 25 the adhesive was applied from asolution in a blend of aromatic and aliphatic hydrocarbons. A coatingweight of about 1.2 oz./sq. yd. was used. The resulting tape was slitinto rolls 2% inches wide, suitable for preparation of diaper tape tabs.

EXAMPLE 2 A 54 lb./ 3,000 sq. ft. base paper made from bleached kraftfiber was saturated with 50 parts of the following formulation for every100 parts of fiber.

Rhoplex B (trademark-Rohm and Haas Co.)

100 Aquapel 8-380 (trademark for an alkylketene dimer sizing agent soldby Hercules, Inc.) 1

The saturated base was subsequently coated with backsize, releasecoating, and adhesive as in Example 1.

EXAMPLE 3 A commercially available pressure-sensitive tape submitted bythe supplier as a potential diaper tape. This example is included toillustrate the need for surprisingly high physical strength. The tapeconsisted of a unified and release-coated paper backing and arubbet-based adhesive. While the adhesive characteristics weresatisfactory, the tape failed in use tests.

EXAMPLE 4 An experimental adhesive containing excessive extension oil,and applied to the same base paper of Example I, also failed in usetests. The adhesive formulation used was:

Kraton I107 I00 Sta-Tac IOO I CAO-l (trademark for antioxidant-CatalinCorporation of America) 2 Sunthene 3120 100 I-Iydral 705 (trademark forhydrated alumina- Aluminum Corporation of America) 25 This adhesive issubstantially softer than that of Examples I and 2, which provides ahigh level of resistance to peel from polyethylene film when appliedwith little pressure and peeled manually. It also retains considerableshear resistance when measured by PSTC-7, but does not providesufficient holding power when a peel component is introduced in theshear test.

This adhesive was evaluated with laboratory samples, coded 4a, using thesame base as in Example I, but without backsize or release coatings. Fordirect comparison, the adhesive of Example 1 was applied in the same wayto the same uncoated base, and coded 4b. Since the physical strength ofthe tapes is derived almost entirely from the backing, physicalproperties of these samples were not measured.

TABLE I PHYSICAL PROPERTIES Ex. Ex. Ex I 2 3 Basis Wgt.lbs./3000 sq. ft.I24 ll8 Caliper-mils 8 8 7 CD Tensile lbs/inch width 22.9 29.2 15.2 (Iinch span, constant rate of elongation at 200%lmin.) CD Elongation 21 l716 MD Finch Edge Tear lbs. I5.3 3l.l 14.8 MD Elmendorf Tear- I38 I22g./I6 Sheets Delamination Resistance 28 22 30 oz./inch width TABLEII.ADHEBIVE TESTS Qluck- Adheslve Adhesion stick to Panel Holding Wt.(oz./ to PE PE adhesion power (80 sq. yd.) (oz./In.) (0z./:ln.) (ea/In.)shear)(mln.)

Example 4Wetmils.

Methods for preparing such tapes are well known. Basically, thepreferred procedure is to coat the base with the backsize, dry it at 2251F and then apply the release coating. The release coated material isdried and cured at an elevated temperature (eg 350-400 F). The adhesiveis then applied, and the product is wound into rolls. Conventionalequipment such as reverse roll or knife-over-roll coaters, dryers, etc.may be used as is well known in the art.

Referring to FIG. 1, adhesive tape 10 includes base 12, backsize 14,release coat l6, and pressure sensitive adhesive 18.

FIGS. 2 and 3 illustrate a disposable diaper incorporating the pressuresensitive adhesive tape of this invention. Diaper 20 may be ofconventional construction comprising a main absorbent pad 22 consistingof wood pulp fluff, layers of cellulose wadding, absorbent cottonfibers, and the like. Pad 22 has a thin, impervious backing 24 which maybe typically pigmented and embossed 1 mil polyethylene. The outersurface of the film backing 24 may be treated by corona discharge or thelike so as to be more receptive to adhesive. Film backing 24 is usuallyat least coextensive with pad 22 but preferably extends around the edgesof the pad and partially overlaps the top of the pad. The top surface ofthe pad 22 is covered with a fluid pervious sheet 26 which is usually ofnonwoven construction and may be hydrophilic or hydrophobic. Cover sheet26 may be attached to film backing 24 either on top of the overlappingedge as shown in FIG. 3 or underneath the overlapping edge. In otherconstructions cover sheet 26 may extend around the sides of pad 22 andbe attached on the bottom side of the diaper either over or under filmbacking 24, or cover sheet 26 and film backing 24 may extend beyond thediaper edges and be heat sealed together.

Near one end of the diaper 20 and at opposite edges thereof are attachednarrow strips 28 of the pressure sensitive adhesive tape with one endextending beyond the respective edges of the diaper. The pressuresensitive adhesive coating 18 on the surface of these extensions iscovered by protective cover strip 30. Cover strip 30 is usually widerand longer than tape 10 to provide a convenient handle for removal. Theinwardly disposed end of the cover strip preferably extends over theface of the diaper.

The pressure sensitive adhesive composition may be varied within certainranges to insure that an adequate adhesive force is obtained. Thus, inExample 1, using 100 parts by weight of the block copolymer (Kraton1107) as the basis; the amount of tackifier may be in the range of from75 to 150; and the antioxidant in the range of from 0.5 to 3.0; theextension oil in the range from 10 to 75 parts; and the filler in therange from to 50 parts all by weight.

The amount of saturant used in the fibrous backing may be within therange of from about 20 to about 80 dry parts of fiber with the range offrom 35 to about 65 being preferred based on cost and performancecharacteristics. Additional examples of suitable saturants includel-lycar 2671' (trademark) from B. F. Goodrich and Rhoplex P-206(trademark) from Rohm and Haas.

The backsize may be pigmented with up to 100 parts pigment per 100 partsresin, if desired, and preferably includes 20 to 65 parts of a suitablepigment such as titanium dioxide, carbonates, and clay, for example.

Similarly the ingredients of the backsize may be varied, using from 50to 150 parts of the polyacrylate for every 100 parts of polyvinylchloride, depending on the pigment level utilized. Also the actualweight of coating may be varied from about to 25 lbs/3,000 sq. ft. Whilethe preferred polyacrylate is that identified as Rhoplex B15, otherssuch as those disclosed in U.S. Pat. No. 3,066,043 may be utilized aswell.

The ingredients of the release coating can also be varied within thelimitations of release level desired while assuring adequate cure toprevent transfer to the adhesive.

A suitable protective release strip for the pressure sensitive mass onthe ends of the strip which extend beyond the edge of the diaper 13 ispreferably polyethylene film which may vary in thickness within therange 3-6 mils. The film preferably has a release coat e.g. a coatingbased on silicone. Other fairly rigid films such as polypropylene,polyesters, and polyvinyl chloride may also be used as the protectivecover sheet as well as silicone coated glassine type paper.

Extensive testing of the tape of this invention under actual useconditions indicates that attachment strengths greater than required totear 1 mil polyethylene film diaper backing are consistently obtained.The failure rate in use of the tape of the invention was less than 0.2percent in 800 tests.

While the pressure sensitive adhesive tape of the invention has beendescribed with reference to specific embodiments and to disposablediaper applications, other embodiments and uses will suggest themselvesto those skilled in this art wherever a strong, inexpensive pressuresensitive tape is required.

I claim:

l. A strong pressure sensitive adhesive tape which has excellentadhesion to polyethylene film comprising a reinforced fibrous backing,

a backsize coating of polyvinyl chloride plasticized with a polyacrylateon one side of said backing,

a release coating of silicone rubber over said backsize, and

an adhesive coating on the side of said backing opposite from saidbacksize and release coatings, said adhesive comprising an aggressivelytacky block copolymer of isoprene and styrene tackified with apolyolefin.

2. The tape of claim 1 wherein said backing has a basis weight in therange of 50 to 120 lbs/3,000 ft? and is saturated with 20 to parts/parts fiber of polyacrylate binder.

3. The tape of claim 1 wherein said backing is a unified paper includingKraft fibers beater treated with acrylonitrile rubber.

4. The tape of claim 2 wherein said backsize coating comprises thefollowing proportions of ingredients: 100 parts polyvinyl chloride, 50to parts polyacrylate, and 30 to parts titanium dioxide.

5. The tape of claim 3 wherein said backsize further includes about 20to 65 parts of a decorative pigment per 100 parts of resin and isapplied in the amount of about 10 to 25 lbs. per 3,000 sq. ft.

6. The tape of claim 4 wherein the adhesive is applied in the amount ofabout 0.8 to 1.8 oz. per square yard and comprises, in parts by weight:

Block copolymer 100 parts Polyolefin tackifier 75 to 150 partsAntioxidant 0.5 to 3.0 parts Naphthenic oil 10 to 75 parts Filler 0 to50 parts 7. A diaper tape adapted for use as fasteners with disposablediapers of the type combining an absorbent pad with a fluid perviouscover and a fluid impervious thin film backing comprising,

a reinforced fibrous backing,

a backsize of from 10 to 20 lbs/3,000 sq. ft. of pigmented polyvinylchloride plasticized with a polyacrylate on one side of said backing,

a release coat of from 0.1 to 1.0 lbs/3,000 sq. ft. of catalyst-curedsilicone rubber over said backsize, and

an adhesive on the side of said backing opposite from said backsize andrelease coat, said adhesive comprising an aggressively tacky blockcopolymer of isoprene and styrene tackified with a polyolefin.

8. An improved disposable diaper of the type having an absorbent padwith a fluid-pervious cover, a fluidimpervious thin film backing, andpressure sensitive adhesive tape fastening means, the improvementwherein said pressure sensitive adhesive tape comprises,

a reinforced fibrous backing,

a backsize coating of polyvinyl chloride plasticized with a polyacrylateon one side of said backing,

a release coating of catalyst-cured silicone rubber over said backsize,and

an adhesive coating on the side of said backing opposite from saidbacksize and release coatings, said adhesive comprising an aggressivelytacky block copolymer of isoprene and styrene tackified with apolyoletm, and extended with a naphthenic oil.

9. The diaper of claim 8 wherein said tape backsize coating is appliedin the amount of about 10 to 25 lbs/3,000 ft. and comprises thefollowing proportions of ingredients: 100 parts polyvinyl chloride, 50to 150 parts polyacrylate, and 30 to 195 parts pigment.

10. The diaper of claim 9 wherein said tape adhesive is applied in theamount of from about 0.8 oz. to 1.8 oz. per square yard and comprises,in parts by weight:

Block copolymer 100 parts Polyolefin tackifier 75 to 150 partsAntioxidant 0.5 to 3.0 parts Naphthenic oil 10 to 75 parts Filler 0 to50 parts

2. The tape of claim 1 wherein said backing has a basis weight in therange of 50 to 120 lbs./3,000 ft.2 and is saturated with 20 to 80parts/100 parts fiber of polyacrylate binder.
 3. The tape of claim 1wherein said backing is a unified paper including Kraft fibers beatertreated with acrylonitrile rubber.
 4. The tape of claim 2 wherein saidbacksize coating comprises the following proportions of ingredients: 100parts polyvinyl chloride, 50 to 150 parts polyacrylate, and 30 to 195parts titanium dioxide.
 5. The tape of claim 3 wherein said backsizefurther includes about 20 to 65 parts of a decorative pigment per 100parts of resin and is applied in the amount of about 10 to 25 lbs. per3, 000 sq. ft.
 6. The tape of claim 4 wherein the adhesive is applied inthe amount of about 0.8 to 1.8 oz. per square yard and comprises, inparts by weight: Block copolymer - 100 parts Polyolefin tackifier - 75to 150 parts Antioxidant - 0.5 to 3.0 parts Naphthenic oil - 10 to 75parts Filler - 0 to 50 parts
 7. A diaper tape adapted for use asfasteners with disposable diapers of the type combining an absorbent padwith a fluid pervious cover and a fluid impervious thin film backingcomprising, a reinforced fibrous backing, a backsize of from 10 to 20lbs./3,000 sq. ft. of pigmented polyvinyl chloride plasticized with apolyacrylate on one side of said backing, a release coat of from 0.1 to1.0 lbs./3,000 sq. ft. of catalyst-cured silicone rubber over saidbacksize, and an adhesive on the side of said backing opposite from saidbacksize and release coat, said adhesive comprising an aggressivelytacky block copolymer of isoprene and styrene tackified with apolyolefin.
 8. An improved disposable diaper of the type having anabsorbent pad with a fluid-pervious cover, a fluid-impervious thin filmbacking, and pressure sensitive adhesive tape fastening means, theimprovement wherein said pressure sensitive adhesive tape comprises, areinforced fibrous backing, a backsize coating of polyvinyl chlorideplasticized with a polyacrylate on one side of said backing, a releasecoating of catalyst-cured silicone rubber over said backsize, and anadhesive coating on the side of said backing opposite from said backsizeand release coatings, said adhesive comprising an aggressively tackyblock copolymer of isoprene and styrene tackified with a polyolefin, andextended with a naphthenic oil.
 9. The diaper of claim 8 wherein saidtape backsize coating is applied in the amount of about 10 to 25lbs./3,000 ft.2 and comprises the following proportions of ingredients:100 parts polyvinyl chloride, 50 to 150 parts polyacrylate, and 30 to195 parts pigment.
 10. The diaper of claim 9 wherein said tape adhesiveis applied in the amount of from about 0.8 oz. to 1.8 oz. per squareyard and comprises, in parts by weight: Block copolymer - 100 partsPolyolefin tackifier - 75 to 150 parts Antioxidant - 0.5 to 3.0 partsNaphthenic oil - 10 to 75 parts Filler - 0 to 50 parts